JPH0569686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multilayer parison forming method and apparatus in blow molding.

Conventional technology To form a multilayer parison in conventional blow molding, plasticized resin is fed into a head using an extruder, and the multiple layers of an inner layer parison and an outer layer parison are laminated by successively merging in the head, and the exit A multilayer parison was formed by extrusion through a slit, and this was blow molded in a mold. Blow molding is used to mold small food containers with gas and barrier properties, cosmetic bottles with good appearance, etc., but when molding large products such as automobile gasoline tanks, gas and barrier properties are The focus was on the development of a multi-layer gasoline tank, which could not be formed using extrusion molding as the size of the product increased, and high-speed parison molding was required. To ensure high speed and accurate parison wall thickness distribution, multilayer heads have been implemented as an intermittent multilayer parison forming process in which each layer is extruded with a ring plunger.

Problems to be Solved by the Invention However, among conventional blow-molded products, small products such as cosmetic bottles had good skin, but large molded products had poor skin and poor appearance. . One method to improve the skin is multilayer molding using a multilayer parison that combines an outer layer resin with good surface properties (mainly low viscosity) and an inner layer resin (high molecular weight, high viscosity) with drawdown resistance. The reason why it was bad was as follows. That is, in order to prevent drawdown, it is necessary to extrude the parison from the head quickly, but since the inner layer resin and outer layer resin are merged in the head and extruded as multiple layers from the exit slit, the flow of the laminated layers from the merge section to the exit slit is prevented. However, when this laminated layer is extruded at high speed, turbulence occurs in the laminated flow, and once the high-viscosity inner layer resin adheres to the wall surface where the low-viscosity outer layer resin is flowing, the adhesive force of the inner layer resin is strong, so it cannot be easily removed and the tail will be formed. It was not possible to obtain a parison with good pulling texture, and in addition, the extrusion of the parison was intermittently due to extrusion using a ring plunger developed for extrusion at high speed, which is an essential method for large-scale molding, and the extrusion of the parison was intermittently, and the extrusion of the parison was not possible until the exit slit. The reason for this is that the flow of the layers is even more disturbed.

The present invention reduces the viscosity difference between the inner layer parison and the outer layer parison to be laminated, and the tension due to the expansion of the inner layer parison that occurs when the inner layer parison is extruded at high speed.
The extension part is provided along the swell shape at the part where the inner layer parison, which is used for the lamination pressure against the outer layer parison and is pushed out into the atmosphere from the inner layer exit slit without performing confluence lamination inside the head, expands due to the ballast effect. By providing an exit slit for the outer layer parison, the laminated state of the multilayer parison is improved, and the outer layer is made of a resin with good surface properties such as smoothness, texture transferability, and paintability, and a high molecular weight resin with drawdown resistance.・By extruding a multilayer parison with high viscosity resin as the inner layer (main material) at high speed and intermittently, large blow molded products with beautiful skin can be produced. This invention aims to effectively mold a multilayer parison with a thickness of one-third or less.

Means for Solving the Problems In the present invention, the resin for the inner layer and the resin for the outer layer are extruded separately and close to each other from the head main body 1 to the outside, and when the resin for the inner layer and the resin are extruded, a balance effect of the inner layer parison occurs. In order to stack the outer layer parison on the inner layer parison on the outside of the head body 1 using lamination pressure, a ring 5 or die 6 attached to the lower part of the head body 1 is fitted into the head body 1 so as to be movable up and down. A chamber 33 is formed between the ring plunger 2 and the flow bin 4,
A trapezoidal core 8 is attached to the lower end of the flow bin 4, and an inner layer outlet slit portion 15 communicating with the chamber 33 is directed downwardly and outwardly between the core 8 and the lower end of the ring 5 or the lower end of the die 6. Furthermore, an outer layer outlet slit portion 18 is formed between the die 6 and the die tip support 7 in proximity to the inner layer outlet slit portion 15, and when the inner layer resin is extruded from the inner layer outlet slit portion 15, the inner layer Taper 1 along the swell shape that occurs in the parison
6 is extended to the outlet of the outer layer outlet slit portion 18.

According to the present invention, the inner layer resin stored in the lower chamber 33 of the head body 1 exits from the inner layer outlet slit portion 15 to the outside of the head body 1 to form the inner layer parison, and is shaped into a swell due to the ballast effect. The outer layer resin has an outer layer outlet slit portion 18.
At the same time, due to the stacking pressure generated by the ballast effect of the inner layer parison and the taper 16 extending to the exit of the outer layer outlet slit section 18, the outer layer parison has the swell shape of the inner layer parison. are stacked along the

Example Embodiments of the present invention will be described with reference to the drawings.

Example 1 Figure 1 shows the molding of a two-layer parison made of a melt-adhesive resin, for example, using a polyolefin resin as the base material and the outer layer being a resin of the same type with improved appearance or an elastomer resin of the same type. Furthermore, it is a laminated part of a device that uses materials such as polymer alloys.

Reference numeral 1 denotes a cylindrical head main body, and a first annular passage 30 through which the inner layer resin passes is bored in the upper part of the inner surface, and the first annular passage is connected to a main extruder 21 installed outside the head main body 1.
It communicates with the opening 21a of. Further, a ring plunger 2 is fitted coaxially in the head main body 1 so as to be movable up and down, leaving a narrow passage 31 communicating with the first annular passage 30, and a guide plunger 3 coaxially fitted in the ring plunger 2. A flow pin 4 is fitted through the flow pin 4 so as to be movable up and down, and a ventilation passage 32 is formed in the center of the flow pin 4. Reference numeral 5 denotes a ring attached to the lower end of the head body 1, and a die 6 is attached to the lower part of the ring 5 via a heat insulating material 13. The heat insulating material 13 is effective in reducing heat conduction because it sets the temperatures of the resins in the inner layer and the outer layer to appropriate temperatures. Further, a truncated conical core 8 is fixed to the lower end of the flow bin 4, and the core 8 has a ventilation passage 3.
An exhaust port 8a communicating with 2 is bored. and a flow bin 4, a guide plunger 3, a peripheral ring 5 at the lower end of the ring plunger 2, and a die 6.
A chamber 33 serving as a resin passage is formed between the inner surface of the core 8 and the surface of the core 8, and the cross section is 8 mm in the direction along the swell shape when the inner layer parison is extruded following the chamber 33. Inner layer outlet slit portions 15 are formed radially downward and outward, and are shaped to become gradually narrower toward the lower end. 7 is a die tip support that is concentric with the outer diameter of the lower part of the die 6 and is attached to the lower part of the die 6, and includes a second annular passage 34 through which the outer layer resin passes between the inner surface of the die 6 and the outer surface of the die tip support 7; A cylindrical passage 18 communicating with the passage is formed. Further, an adjustment ring 10 is fitted into the inner surface of the die tip support 7, and the eccentricity of the gap is adjusted by this adjustment ring 10. Reference numeral 9 denotes a die tip, which is attached to the lower surface of the die tip support 7 by a holding ring 14, and has a cylindrical resin passage 18 and an inner layer outlet slit on the upper surface of the die tip 9, which are in contact with the adjustment ring 10 and whose inner upper part serves as an outer layer outlet slit. The lower part of the inner surface is formed into a tapered part 16 close to the outlet of the section 15 so as to be an extension of the inner layer outlet slit section 15, i.e., the outer layer is pushed out from the cylindrical channel 18 via the second annular channel 34. The parison is formed in a shape that allows it to be laminated properly along the shape of the inner parison that exits from the chamber 33 through the inner layer outlet slit portion 15 and expands due to the swell effect. The second annular passage 34 is connected to the sub-extruder 2 installed outside the die 6.
Opening 19a of Achim letter 19 connected to 0
It is connected to. A core chip 11 and an adjustment bolt 12 are provided on the lower surface of the core 8.
Accordingly, the eccentricity can be adjusted from the inside of the inner layer outlet slit portion 15. 22 is Achim letter 1
9 is an internal plunger, 23 is an inner layer cylinder that raises and lowers the ring plunger 2 to extrude the inner layer resin, 24 is a parison control cylinder, and 25 is a plunger 22 for extruding the outer layer resin in the sub-extruder 20. It is an actuator to operate.

Next, the operation of Example 1 will be explained.

The resin plasticized by the main extruder 21 and extruded from the opening 21 a is forced to flow downward from the first annular passage 30 of the head body 1 through the narrow passage 31 and is fed into the chamber 33 . Depending on the amount of resin for the inner layer fed into the chamber 33, the ring plunger 2 arranged coaxially moves the cylinder 23 for the inner layer.
When the ring plunger 2 is lowered by the inner layer cylinder 23, the resin in the chamber 33 is pushed out of the head body 1 through the inner layer outlet slit 15. Adjustment bolt 12 at the bottom of core 8
Since the thickness distribution on the circumference is adjusted to be uniform, the resin passing through the inner layer exit slit portion 15 has a uniform thickness and forms a swell shape while expanding due to the ballast effect. It is extruded as an inner layer. On the other hand, the resin that will become the outer layer is plasticized in the sub-extruder 20 and transferred to the accumulator 1.
The actuator 25 is set in conjunction with the inner layer cylinder 23 and operates synchronously to push out the outer layer resin in the accumulator 19. The resin for the outer layer is the second layer.
It is extruded through the annular passage 34 and the cylindrical passage 18, and at this time it is extruded from the inner layer outlet slit part 15, but at this time, the resin for the inner layer that has been extruded from the inner layer outlet slit part 15 is laminated on the swell-shaped surface. Therefore, the resin for the outer layer, that is, the surface of the outer layer parison, conforms to the swell shape of the inner layer parison along the lapper-shaped taper 16 of the die chip 9, and is beautifully laminated and continuous without being collapsed by the lamination pressure of the inner layer parison. Then, he is pushed out.

Embodiment 2 The device shown in FIG. 3 is a three-layer parison molding device, in which the inside of the ring 5 itself attached to the lower end of the head body 1 of the two-layer parison molding device shown in FIG. 1 is bulged. A chamber 3 is formed between the bulge 5a and the ring plunger 2, guide plunger 3, and flow bin 4.
3 and between the lower surface 5b of the bulge 5a and the outer surface 8b of the core 8.
Subsequently, an inner layer outlet slit portion 15 is formed which has a figure-eight cross section and is shaped so that it becomes gradually narrower toward the lower end. Further, a third annular passage 35 for the intermediate layer or adhesive layer and a cylindrical passage 18 communicating with the third annular passage 35 serving as an outer layer outlet slit are formed between the lower part of the ring 5 and the die 6, and the third annular passage 35 is connected to a sub-extruder 20 for the material for the intermediate layer or adhesive layer, which is installed outside the die 6. A spacer 26 is attached to the lower part of the die 6, and a second annular passage 34 for the outer layer resin and an outer layer resin passage 29 communicating therewith are formed between the die 6 and the spacer 26. It is communicated in the middle of the cylindrical passage 18. Said second
The annular passage 34 is connected to an extruder (not shown) installed outside the head body 1. spacer 2
An adjustment ring 10 is fitted into the inner surface of the die tip support 7 attached to the lower part of the die tip support 6. Reference numeral 9 denotes a die chip attached to the lower surface of the die tip support 7 by a presser ring 14. The upper inner surface constitutes the lower end of the cylindrical resin passage 18, and the lower inner surface is formed into a taper 16.

To explain the effect of Example 2, Example 1
Similarly, the inner layer resin in the chamber 33 is extruded to the outside from the inner layer outlet slit portion 15, and the resin for the intermediate layer or adhesive layer is extruded by the sub-extruder 20 through the third annular passage 35 into the cylindrical resin passage 18. The resin for the outer layer is extruded to the outside by an extruder (not shown), passes through the second annular passage 34, passes through the outer layer resin passage 29, and merges with the resin for the intermediate layer that has been pressure-flowed from the cylindrical passage 18 to the outside. is pushed out. Then, when the inner layer resin is extruded to the outside and becomes the inner layer parison, it forms a swell shape, and the outer layer parison, in which the intermediate layer resin and outer layer resin that have been extruded at the same time merge and are laminated, is laminated on the surface of the swell shape. Therefore, the surface of the outer layer parison conforms to the swell shape of the inner layer parison along the taper 16 of the die chip 9, and is neatly stacked without being destroyed by the stacking pressure of the inner layer parison to form a three layer parison.

Effects According to the present invention, the high viscosity inner layer resin and the low viscosity outer layer resin are exposed to the atmosphere separately and in close proximity from the head body, without merging the laminated layers of the multilayer parison inside the head body. Since extrusion and lamination are performed immediately after extrusion, there is no melt fracture, which was a problem on the flow path from the merging part to the exit slit when merging in the conventional head body, and there are no viscosity restrictions on the selection of the outer layer resin. It is possible to mold high-quality multilayer parisons. In addition, the stacking pressure generated by the Pallas effect of the inner layer parison during stacking is utilized, and the taper formed in the extended portion near the outer layer exit slit section is designed to reduce the pressure caused by the expansion of the inner layer parison (Pallus effect) or the stacking pressure. Both can be effectively crimped together without protecting the outer layer parison and causing deformation or the like. Furthermore, the outer layer resin can be extruded at a high temperature with good surface properties, and in combination with effective and accurate lamination of the outer layer parison to the inner layer parison, a product with an excellent appearance can be molded. In addition, the present invention is an effective means for laminating a thin outer layer resin onto an inner layer resin that has a base resin, and since the expansion rate of the inner layer parison due to the paras effect is constant under the same resin pressure, the pressing force against the outer layer parison is constant. This makes it possible to maintain good lamination strength and contribute to the molding of good products. In addition, in the present invention, the high viscosity of the inner layer resin as in the conventional case of convergence within the head body,
The high viscosity of the outer layer resin corresponding to high resin pressure and the extrusion force of high resin pressure are not required, and the outer layer resin can be extruded at low pressure, so the apparatus can be made extremely compact. A further noteworthy advantage is that the difference in viscosity between the resins does not become a problem when the layers are combined. Therefore,
The inner layer resin, which serves as the base material, has a high viscosity with drawdown resistance in a low temperature range, and the outer layer resin has a low viscosity temperature setting and material in a high temperature range to improve smoothness, grain transferability, and paintability. The inner layer resin can be freely set with an emphasis on drawdown resistance.
Furthermore, since the problem of appearance, which was considered to be a weak point of blow molding, has been solved, useful large-sized blow molded products can be widely provided at low cost.

In addition, the resin used as the outer layer resin to improve the surface is about 3 to 5 times more expensive than the ultra-high molecular weight polyethylene used as the base material, but in the present invention, the outer layer resin is less than one third of the inner layer resin. Since it is possible to form a multilayer parison with a thickness of

[Brief explanation of the drawing]

The drawings show embodiments of the present invention. Fig. 1 is a sectional view of a two-layer parison forming apparatus of Embodiment 1, and Fig. 2 is an enlarged sectional view of the lower part of the head body of the apparatus shown in Fig. 1, showing the inner layer. and shows a state in which outer layer parisons are stacked. FIG. 3 is an enlarged sectional view of the lower part of the head main body of the three-layer parison forming apparatus of Example 2. Symbols; 1...Head body, 2...Ring plunger, 3...Guide plunger, 4...Flow bin, 5...Ring, 5a...Bulging portion, 5b...
... lower surface, 6 ... die, 7 ... die tip support, 8 ... core, 8a ... exhaust port, 8b ... outer surface, 9 ... die chip, 10 ... adjustment ring, 1
1...core chip, 12...adjustment bolt, 13...
...Insulating material, 14... Holding ring, 15... Inner layer outlet slit portion, 16... Taper (tupular inner surface), 18... Outer layer outlet slit portion (cylindrical passage), 19... Achim letter, 19a... Opening ,
20...Sub-extruder, 21...Main extruder, 21a...
... Opening, 22 ... Plunger, 22a ... Chamber, 23 ... Cylinder for inner layer, 24 ... Control cylinder for parison, 25 ... Actuator (of plunger 22), 26 ... Spacer, 27 ... Outer layer inlet, 28 ...resin passage,
29... Outer layer resin passage, 30... First annular passage,
31... Narrow passage, 32... Ventilation passage, 33... Chamber, 34... Second annular passage, 35... Third annular passage, A... Inner layer parison, B... Outer layer parison.

Claims (1)

[Scope of Claims] 1. The resin for the inner layer and the resin for the outer layer are extruded from the head body 1 to the outside separately and in close proximity, and when the resin for the inner layer is extruded, the lamination pressure generated by the balancing effect of the inner layer parison is reduced. A multilayer parison forming method in blow molding, characterized in that an outer parison layer is laminated on an inner layer parison layer on the outside of a head body 1. 2. A chamber 33 is formed between the ring 5 or die 6 attached to the lower part of the head body 1 and the ring plunger 2 and flow bin 4 fitted in the head body 1 so as to be able to move up and down.
A trapezoidal core 8 is attached to the lower end, and an inner layer outlet slit portion 15 communicating with the chamber 33 is formed downwardly and outwardly between the core 8 and the lower end of the ring 5 or the lower end of the die 6. Further, an outer layer outlet slit portion 18 is formed between the die 6 and the die tip support 7 close to the inner layer outlet slit portion 15, and the inner layer resin is formed in the inner layer outlet slit portion 15.
A multilayer parison forming apparatus for blow molding, characterized in that a taper 16 that follows the swell shape produced in the inner layer parison when extruded from the outer layer extends to the exit of the outer layer exit slit section 18.